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Water pollution mechanisms caused by bottom sediments in limnology and coastal waters and methods for improving water environments

湖沼和近岸海域底质沉积物造成的水污染机制及水环境改善方法

基本信息

批准号：
12450201
负责人：
KANDA Tohru
金额：
$ 7.1万
依托单位：
Kobe University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

This research deals with mechanisms of water pollution caused by bottom sediments in various waters and examines methods for improving the water environments in these waters. Main results are summarized as follows.The effect of diffusional mass transfer between bottom sediment and overlying water were investigated theoretically and experimentally. The models to estimate the vertical diflusive flux at the sediment/water interface were formulated for smooth bed, rough bed and turbulent flow in a rectangular concave. Moreover, to investigate flow structures over such bed forms, the turbulent flows in the concave were measured by using a PIV and analyzed by employing a wavelet transform and a proper orthogonal decomposition.A plume generated from a sloping boundary of constant buoyancy was investigated experimentally and theoretically. A theoretical model was developed assuming a self-similar flow structure. Solutions for buoyancy and velocity fields were successfully obtained. The agreement between the analysis and experiments was quite satisfactory. The analysis enables us to quantitatively estimate water quality transport caused by the plume in a reservoir.To clarify the cycling of nutrient salts in river estuary, field observations were carried out in Osaka Bay area. Results show that 20% of the amounts ofTP and TN supplied from the upstream have settled in the lower reaches of the river, and that most of the organic substances have settled in the area of lOknroflshore from the river mouth. It has been understood that the denitrification phenomenon is playing an important role of a removal of nitrogen in the estuary.The characteristic of tidal current at Maiko beach was investigated through field data. The eastern direction flow due to the pressure gradient was prominent there and it had a major effect to sediment transport. Then, A numerical method to simulate a run-up over a sloping bed profile was proposed.

本研究探讨各种沃茨底质造成水污染的机制，并探讨改善这些沃茨水环境的方法。主要研究结果如下：从理论和实验两方面研究了底质与上覆水之间的扩散传质效应。建立了光滑床面、粗糙床面和矩形凹腔紊流情况下的泥沙/水界面垂向扩散通量计算模型。采用PIV技术对凹床内的湍流流动进行了测量，并采用小波变换和正交分解方法对凹床内的湍流流动进行了分析，对等浮力倾斜边界产生的羽流进行了实验和理论研究.建立了自相似流动结构的理论模型。成功地获得了浮力和速度场的解。分析结果与实验结果吻合较好。分析使我们能够定量地估计在水库的羽流引起的水质传输。为了澄清河口的营养盐的循环，在大坂湾地区进行了现场观测。结果表明，上游输入的TP、TN有20%沉降在下游，有机物大部分沉降在河口近岸。通过实测资料，研究了舞古海滩的潮流特征。压力梯度引起的东向流在该区域表现突出，对泥沙输移有重要影响。在此基础上，提出了一种数值模拟斜坡床面起动的方法。